The present invention relates to a glass panel for fire protection and, in particular, to such a glass panel having nonshattering property as well as fire resistant or fireproof property.
In order to prevent the spreading of fire, a door, a window, or a partition wall are made of fire resistant or fire proof materials, for example, iron or steel. However, iron and steel are not light transparent and are, therefore, not desired for the window. Further, the door and the partition are often desired to be made of light transparent materials.
As a glass material for use in fire protection doors, windows, partitions and other fire protection structures, a fireproof or fire resistant glass plate is known in the art. A typical one of the fireproof glass plate is a wire glass which is a sheet glass with woven wire mesh embedded in the center of the sheet. Another type of the fireproof glass plate is made of a heat-resistant and light transparent crystallized glass plate. As one of the crystallized glass, "Fire Lite" glass plate which is made by Nippon Electric Glass Company Limited, a corporation in Japan, and is available in commerce. The crystallized glass consists of 3-5 wt. % Li.sub.2 O, 20-35 wt. % Al.sub.2 O.sub.3, 55-70 wt. % SiO.sub.2, 1-3 wt. % TiO.sub.2, 1-4 wt. % ZrO.sub.2, 1-5 wt. % P.sub.2 O.sub.5, 0-4 wt. % Na.sub.2 O, and 0-4 wt. % K.sub.2 O, but a total amount of Na.sub.2 O and K.sub.2 O being 0.5-4 wt. %. The crystallized glass contains the beta-quartz or beta-eucriptite solid solution crystals. The crystallized glass is disclosed as a heat resistant glass in U.S. Pat. No. 3,282,712. The crystallized glass plate has been tested according to the Notification No. 1125 of the Ministry of Construction of Japan and allowed to be used as a fireproof glass for use in a fire protective door, window, partition and other fire protections.
A conventional soda glass plate is low in mechanical impact resistance and in thermal shock. Therefore, it is readily broken and shattered by impact or shock. A safety glass is also known in the art which is improved in the mechanical strength and has nonshattering property. As typical safety glasses, there is known a laminated glass and a glass covered with a thin plastic film. However, such safety glasses do not provide fire protection. Although the wire glass is effective as a safety glass, it tends to broken by a certain strength of mechanical impact to form a through hole. Therefore, the wire glass is not sufficient for the safety glass.